Ni/YBa2Cu3O7−x and Ni/Bi2Sr2Ca0.8Y0.2Cu2Ox interface formation: Reactivity, segregation, and chemical trapping

Abstract

Interfaces formed by condensing Ni atoms onto YBa2Cu3O7−x (Y-123) and Bi2Sr2Ca0.8Y0.2Cu2Ox (Bi-2212) have been studied with x-ray photoelectron spectroscopy. For both Y-123 and Bi-2212, the Ni 2p3/2 and O 1s core level features indicate Ni–O reactions and changes in the Cu 2p3/2 emission that reflect reduction from nominal Cu2+ to Cu1+ oxidation states. Ni deposition onto Bi-2212 also reduces Bi–O bonding and releases Bi atoms. For Ni/Y-123, analysis of emission intensities as a function of coverage shows that O and Ba intermix in the growing metal overlayer but that Cu is trapped at the buried interface. For Ni/Bi-2212, similar analysis shows O and Bi intermixing but less effective Cu trapping.